This invention relates to vapor processing equipment, and more particularly to means for recycling condensate formed therein to the vapor stream being processed in such equipment, and more particularly yet to fuel processors for generating H2 for H2-fueled fuel cells.
Vapor processors are well known in the art and include a variety of different types of equipment such as chemical reactors, heat exchangers, liquid-gas separators, humidifiers, inter alia. Such processors typically comprise a housing defining a chamber in which a desired process (e.g. chemical reaction, etc.) is carried out. Condensate from the vapor(s) being processed often undesirably forms in the processors and pools in a sump or low area thereof. Condensate pooling can degrade the performance of the processor in a number of ways depending on the nature of the processor. For example, in the case of a reactor for chemically reacting one vapor with another, or with a gas, loss of some of the vapor as condensate can upset the stoichiometry of the vapor phase reaction which, in turn, can significantly impact the efficiency or yield from the reaction. Moreover, when condensate forms or later evaporates in such reactors, control of the reactor becomes extremely difficult because of the constantly varying conditions.
The presence of a pool of condensate can cause other disruptions as well. One particularly undesirable disruption occurs in the operation of fuel processors that convert liquid hydrocarbons to hydrogen for fueling electrochemical fuel cells used for motive power applications (e. g. vehicle propulsion). One such fuel processor, for example, is described in U.S.Patent Application U.S. Ser. No. 09/187,125 (now U.S. Pat. No. 6,238,815) filed in the names of Glenn Skala, et al. on Nov. 5, 1998, and assigned to the assignee of the present invention. U.S. Ser. No. 09/187,125 (i.e. U.S. Pat. No. 6,238,815) is hereby incorporated herein by reference, in its entirety, and generally relates to a fuel processor for reacting methanol vapor with steam (i.e. a steam reformer) to produce hydrogen for fueling a PEM H2xe2x80x94O2 fuel cell used to propel a vehicle. More specifically, U.S. Ser. No. 09/187,125 (i.e. U.S. Pat. No. 6,238,815) describes a thermally-integrated, two-stage, methanol reformer including a heat exchanger, and first and second catalytic reactors collocated in a common housing in which a vaporous working fluid circulates. In processors such as this, condensate from the working fluid can form on the inside surfaces of the housing and pool in the low sump area(s) of the processor. When the vehicle carrying the fuel processor moves, the condensate pool sloshes back and forth on the floor of the housing which causes some of the condensate to become entrained in the working fluid in the form of liquid droplets. These droplets are then carried into the catalyst by the working fluid which causes a rapid rise in the reaction temperature which, in turn, upsets the reaction kinetics and drives up the amount of carbon monoxide produced by the reaction. Not only does control of the reaction under such circumstances become extremely difficult, but additional means must be provided to remove the additional CO produced before the processor""s effluent can be used in a fuel cell which is intolerant of high concentrations of carbon monoxide. Similar problems can occur in fuel processors used to convert other liquid hydrocarbons (e.g. gasoline) to H2-rich fuel for fuel cells.
The present invention is an inexpensive, refluxing technique for removing any condensate that collects in a sump of a vapor processor and reintroducing it into the vapor stream being processed by that processor.
In its broadest sense, the invention contemplates a vapor processor having an aspirator that removes the condensate from the sump and reintroduces it back into the vapor stream being processed.
According to a preferred embodiment, the invention involves a vapor processor that has a housing defining a chamber for processing a stream of condensable vapor, which chamber has a first region that operates at a first pressure, a second region that operates at a second pressure that is less than the first pressure, and a sump in the first region that collects condensate condensed from the vapor. In accordance with the present invention, an aspirator is provided that communicates the sump with the second region. Because of the pressure difference between the sump and the second region, the aspirator draws condensate out of the sump and transfers it to the second region for reintroduction into the stream. In one embodiment of the invention, the vapor processor is a chemical reactor having a housing that defines a chamber in which a stream of condensable vapors are reacted. The reactor includes a vaporization section which operates at a pressure greater than the first region and in which vapors are formed by vaporizing corresponding liquids thereof that are introduced (e.g. injected) into the vaporization region from outside the reactor. The aspirator communicates the sump with the second region for transferring the condensate from the sump to the second region and thence into the vaporization region of the chamber. Preferably, the aspirator comprises a conduit (e.g. tube) having one end in the sump and the other end in the second region, and the differential pressure between the two is the sole means driving the condensate through the conduit.
A most preferred embodiment of the invention involves a fuel processor for converting a liquid hydrocarbon (HC) fuel to hydrogen.(H2) gas for fueling a fuel cell. The fuel processor includes a housing defining a reaction chamber that contains a catalyst for effecting the HCxe2x86x92H2 conversion, at least one inlet to the housing for introducing the hydrocarbon and water into the housing, and a vaporization section of the chamber adjacent the inlet for converting the liquid hydrocarbon and water to hydrocarbon and water vapors. A fan having a low pressure input side and higher pressure exhaust side draws the vapors into the fan and circulates them throughout the housing. The chamber has a region that operates at a higher pressure than the low pressure side of the fan, a sump in the higher, pressure region that collects condensate condensed from the vapors, and an aspirator that communicates the sump with the low pressure side of the fan for transferring the condensate by differential pressure alone from the sump into the fan and thence into the vaporization section for vaporization therein. More preferably, the fan includes an impeller having a plurality of blades which draw the vapors into its center and discharge them radially outwardly from there, and the aspirator discharges the condensate into the center of the impeller. Most preferably, the fuel processor also has at least one inlet adapted to impinge the hydrocarbon and water onto the impeller in such a manner that the impeller atomizes them in the vaporization section.